A tire is a highly engineered composite designed to provide safety and durability. Tires, in particular automotive tires for passenger cars or aircraft tires for aircrafts, undergo significant dynamic and static stresses and strains in the course of ordinary service life. Performance is critical in this product application due to ramifications of failure while in use. In order to obtain the necessary performance characteristics critical to the proper functioning of a tire, structural reinforcement is a required component of the tire composite. This reinforcement provides many functions in a tire application, in particular overall strength, dimensional stability for the tire and a mechanism to handle stress dissipation during operation (fatigue).
Currently, there is a well established set of products/processes to provide the reinforcing material used in passenger car and truck tire applications.                1. High strength yarn is spun and drawn to produce a continuous filament with engineered physical properties, most notably strength, modulus and shrinkage with different linear densities. High modulus, low shrinkage (HMLS) polyester and rayon are the organic fibers of choice, with HMLS polyester being preferred as carcass reinforcement in passenger car tires.        2. This yarn is then twisted, and multiple twisted ends are plied together to form a cord structure. Twist is imparted to the yarn and cord in order to provide the required fatigue resistance for the reinforcement material in the tire, especially in the sidewall and turn-up region. While the twisting results in improved fatigue performance, it lowers the overall strength and modulus of the cord structure. This twist can be imparted by a) twisting the single yarns in one operation and then plying the twisted single ends into a cord in an other operation, or, b) twisting and plying in the same step by using direct cabling operations.        3. In most applications, these cords are then woven into a fabric where the cords form the warp direction and a higher elongation material is used in the weft-direction to create a stable fabric that will be used as the tire reinforcement. Less frequently, the cords are not woven into a fabric and proceed to the next step in cord form.        
4. The woven fabric (or cord) is then introduced into a chemical/thermal process where a) adhesives are applied to the fabric that promote adhesion of the reinforcement to the rubber compound used in tire manufacture, and b) the fabric is exposed to high temperatures to cure the adhesives and set the final shrinkage, modulus and strength characteristics of the fabric/cord. The fabric (or cord) can then be introduced to the tire manufacturing process where it is combined with rubber to from a rubberized fabric/cord that will constitute the reinforcement component of the tire.
The step(s) that involve(s) twisting and plying is a critical operation in this series of processes. In this step, the proper construction and amount of twist must be established in order to obtain the proper fatigue resistance; however, this must be balanced against the loss in strength and modulus that occurs with twisting/plying as well as the costs for imparting twist, which increase with increasing twist levels. Much effort has been put into developing the proper twist levels to minimize cost and meet key durability requirements.
It has been shown that the twist imparted to the cord structure allows the cord to uniformly dissipate strain during compressive forces, the predominant forces (with respect to fatigue failure) that occur in service. The twist allows the cord to move out of plane during compression, thus avoiding catastrophic failure.
However, the conventional twisted cords suffer from modulus and breaking strength losses due to their helical constructions while having improved flex and compression fatigue resistance. The losses increase with increasing twist-level or helix-angle.